Electrophoretic display apparatus switchable between black-white mode and color mode

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Application Ser. No. 61/619,462 filed Apr. 3, 2012, and Taiwan Application Serial Number 101124938, filed Jul. 11, 2012, the disclosures of which are incorporated herein by reference in their entireties.

BACKGROUND

1. Technical Field

The present invention relates to an electrophoretic display apparatus. More particularly, the present invention relates to an electrophoretic display apparatus switchable between a black-white mode and a color mode.

2. Description of Related Art

Conventional electrophoretic display devices exhibit black-white images and can not provide colorful images. For the purpose of providing colorful images, many researches attempt to add color filters in conventional electrophoretic display devices. However, the pigment or dye in the color filters adsorbs about two-third of incident light so that the brightness of the electrophoretic display devices is significantly decreased. In addition, this kind of electrophoretic display devices exhibits color images only, and can not be switchable between a black-white mode and a color mode. Therefore, there exists in this art a need for a new electrophoretic display apparatus which is capable of resolving these issues.

SUMMARY

According to one aspect of the present disclosure, there is provided an electrophoretic display apparatus switchable between a black-white mode and a color mode. The electrophoretic display apparatus includes an electrophoretic display panel, a light guide, a light source, a light-splitting element and a lens element. The electrophoretic display panel has a display area, which includes a first sub-pixel, a second sub-pixel and a third sub-pixel. The light guide is positioned over the display area, in which the light guide has a light receiving surface and a light emitting surface that faces the display area. The light source is for emitting a light into the light receiving surface, in which the light guide is operable to direct the light towards the display area through the light emitting surface. The light-splitting element is interposed between the light guide and the electrophoretic display panel. The light-splitting element is capable of splitting the light directed towards the display area into a first light beam, a second light beam and a third light beam each having a wavelength different from one another. The first light beam, the second light beam and the third light beam are transmitted in different directions. The lens element is for directing the first light beam, the second light beam and the third light beam to the first sub-pixel, the second sub-pixel and the third sub-pixel, respectively. The lens element is disposed between the light-splitting element and the electrophoretic display panel. When the light source is turned on, the electrophoretic display apparatus is operated in the color mode. When the light source is turned off, the electrophoretic display apparatus is operated in the black-white mode.

It is to be understood that both the foregoing general description and the following detailed description are by examples, and are intended to provide further explanation of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention can be more fully understood by reading the following detailed description of the embodiments, with reference made to the accompanying drawings as follows:

<figref idref="DRAWINGS">FIG. 1A</figref> is a cross-sectional view schematically illustrating an electrophoretic display apparatus according to one embodiment of the present disclosure;

<figref idref="DRAWINGS">FIG. 1B</figref> is a perspective view schematically illustrating a lens element according to one embodiment of the present disclosure;

<figref idref="DRAWINGS">FIG. 1C</figref> is a cross-sectional view schematically illustrating the lens element shown in <figref idref="DRAWINGS">FIG. 1B</figref>;

<figref idref="DRAWINGS">FIG. 2A</figref> is cross-sectional view schematically illustrating an electrophoretic display apparatus according to another embodiment of the present disclosure;

<figref idref="DRAWINGS">FIG. 2B</figref> is a perspective view showing the aspherical lens array according to one example of the present disclosure;

<figref idref="DRAWINGS">FIG. 3A</figref> is a top view schematically illustrating a light-splitting element according to still another embodiment of the present disclosure; and

<figref idref="DRAWINGS">FIG. 3B</figref> is a top view schematically illustrating a light-splitting element according to still another embodiment of the present disclosure.

DETAILED DESCRIPTION

Reference will now be made in detail to the present embodiments of the invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers are used in the drawings and the description to refer to the same or like parts.

In the following detailed description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the disclosed embodiments. It will be apparent, however, that one or more embodiments may be practiced without these specific details. In other instances, well-known structures and devices are schematically shown in order to simplify the drawings.

<figref idref="DRAWINGS">FIG. 1A</figref> is a cross-sectional view schematically illustrating an electrophoretic display apparatus <b>100</b> according to one embodiment of the present disclosure. One feature of the electrophoretic display apparatus <b>100</b> is that the electrophoretic display apparatus <b>100</b> may be operated in two modes, i.e. a black-white mode and a color mode. Specifically, the electrophoretic display apparatus <b>100</b> is switchable between the black-white mode and the color mode. As depicted in <figref idref="DRAWINGS">FIG. 1A</figref>, the electrophoretic display apparatus <b>100</b> includes an electrophoretic display panel <b>110</b>, a collimated light guide <b>120</b>, a light source <b>130</b>, a light-splitting element <b>140</b> and a lens element <b>160</b>.

The electrophoretic display panel <b>110</b> has a display area <b>112</b>, which includes a first sub-pixel <b>112</b>R, a second sub-pixel <b>112</b>G and a third sub-pixel <b>112</b>B. The electrophoretic display panel <b>110</b> may be a microcup electrophoretic display panel or a microcapsule electrophoretic display panel. It is noted that the electrophoretic display panel <b>110</b> does not include conventional color filters having pigment or dye. When the electrophoretic display panel <b>110</b> is operated in the color mode, suitable optical elements are employed to split lights into divided lights with different wavelengths, and each of the divided lights is directed towards a proper sub-pixel such that an originally colorless sub-pixel may exhibit colors, which is described in detail hereinafter. In <figref idref="DRAWINGS">FIG. 1A</figref>, the first sub-pixel <b>112</b>R may be a red sub-pixel, which is illuminated by a red light and thus capable of exhibiting a red color. The second sub-pixel <b>112</b>G may be a green sub-pixel, which is illuminated by a green light and thus capable of exhibiting a green color. The third sub-pixel <b>112</b>B may be a blue sub-pixel, which is illuminated by a blue light and thus capable of exhibiting a blue color.

The collimated light guide <b>120</b> has a light receiving surface <b>122</b> and a light emitting surface <b>124</b>. The collimated light guide <b>120</b> is positioned over the display area <b>112</b> of the electrophoretic display panel <b>110</b>, and the light emitting surface <b>124</b> faces the display area <b>112</b>. The collimated light guide <b>120</b> allows a light L to be emitted from the light emitting surface <b>124</b>, and the transmitting direction of the light L is substantially perpendicular to the light emitting surface <b>124</b>. In one embodiment, the transmitting direction of the light L forms an included angle of less than about 10 degrees with a normal vector of the light emitting surface <b>124</b>. Furthermore, the collimated light guide <b>120</b> allows visible light to be transmitted from the light emitting surface <b>124</b> to a surface opposite thereto.

The light source <b>130</b> is configured to emit a light into the light receiving surface <b>122</b> of the collimated light guide <b>120</b>, in which the collimated light guide <b>120</b> may direct the light towards the display area <b>112</b> through the light emitting surface <b>124</b>. In one embodiment, the light source <b>130</b> includes a red light emitting diode (LED), a green LED and a blue LED. The red LED may emit a light having a principal wavelength of about 600 nm to about 700 nm. The green LED may emit a light having a principal wavelength of about 500 nm to about 600 nm. The blue LED may emit a light having a principal wavelength of about 380 nm to about 480 nm. In the present disclosure, the term “principal wavelength” refers to the wavelength at which a maximum intensity is observed in the spectral distribution of a light. In another embodiment, the light source <b>130</b> may be a laser capable of emitting a white light beam or a LED capable of emitting white light.

The light-splitting element <b>140</b> is interposed between the light guide <b>120</b> and the electrophoretic display panel <b>110</b>, and capable of splitting the light L emitted from the light emitting surface <b>124</b> into a first light beam <b>150</b>R, a second light beam <b>150</b>G and a third light beam <b>150</b>B. Each of the first, second and third light beams <b>150</b>R, <b>150</b>G, <b>150</b>B has a principal wavelength different from that of another one of the first, second and third light beams <b>150</b>R, <b>150</b>G <b>150</b>B. Furthermore, the first, second and third light beams <b>150</b>R, <b>150</b>G, <b>150</b>B are transmitted and travel in different directions. In one embodiment, the light-splitting element <b>140</b> has a plurality of triangular prisms <b>142</b> formed on a surface facing the display area <b>112</b>. The crest line of each of the triangular prisms <b>142</b> is parallel to that of another one of the triangular prisms <b>142</b>. More specifically, the light L has at least three different wavelengths, each having a refractive index different from the others in the triangular prism <b>142</b>, and therefore when the light L passes through the triangular prism <b>142</b>, the light L is split into the first, second and third light beams <b>150</b>R, <b>150</b>G, <b>150</b>B that project to different directions. In one example, the first, second and third light beams <b>150</b>R, <b>150</b>G, <b>150</b>B are respectively a red light beam, a green light beam and a blue light beam. In another example, the triangular prism <b>142</b> is an asymmetrical triangular prism, which has an apex angle of about 70 degrees to about 100 degrees. The width of each of the triangular prisms <b>142</b> may be about 0.5 μm to about 5 μm.

The lens element <b>160</b> is disposed between the light-splitting element <b>140</b> and the electrophoretic display panel <b>110</b>, and capable of directing the first, second and third light beams <b>150</b>R, <b>150</b>G, <b>150</b>B respectively to the first, second and third sub-pixels <b>112</b>R, <b>112</b>B, <b>112</b>B of the electrophoretic display panel <b>110</b>. As described hereinbefore, the electrophoretic display panel <b>11</b> exhibits merely a black color, a white color or a gray color. When the first, second and third light beams <b>150</b>R, <b>150</b>G, <b>150</b>B with certain colors respectively project to the first, second and third sub-pixels <b>112</b>R, <b>112</b>B, <b>112</b>B, the incident lights are reflected by the white pigment particles in the first, second and third sub-pixels <b>112</b>R, <b>112</b>B, <b>112</b>B such that an originally colorless sub-pixels may exhibit colors. Therefore, the electrophoretic display apparatus according to the embodiments disclosed herein may exhibit color images, in which conventional color filters are no longer required. Furthermore, when the light source <b>130</b> is turned on, the light emitted from the light source <b>130</b> travels along the optical path described hereinbefore such that the electrophoretic display apparatus <b>100</b> is operated in the color mode. To the contrary, when the light source <b>130</b> is turned off, the ambient light does not travel along the aforementioned optical path so that the electrophoretic display apparatus <b>100</b> is operated in the black-white mode. Accordingly, one feature of the present disclosure is that the electrophoretic display apparatus <b>100</b> is switchable between the black-white mode and the color mode.

<figref idref="DRAWINGS">FIG. 1B</figref> is a perspective view schematically illustrating a lens element <b>160</b> according to one embodiment of the present disclosure. <figref idref="DRAWINGS">FIG. 1C</figref> is a cross-sectional view showing the lens element <b>160</b> in <figref idref="DRAWINGS">FIG. 1B</figref>. As depicted in <figref idref="DRAWINGS">FIG. 1C</figref>, the lens element <b>160</b> has a first surface <b>160</b><i>a </i>and a second surface <b>160</b><i>b</i>, the first surface <b>160</b><i>a </i>faces the light-splitting element <b>140</b>, whereas the second surface <b>160</b><i>b </i>is opposite to the first surface <b>160</b><i>a</i>. The lens element <b>160</b> includes a plurality of first cylindrical lenses <b>161</b>, a plurality of second cylindrical lenses <b>162</b> and a plurality of third cylindrical lenses <b>163</b>. These first cylindrical lenses <b>161</b> are formed in parallel with each other on the first surface <b>160</b><i>a</i>. The second cylindrical lenses <b>162</b> are formed in parallel with each other on the second surface <b>160</b><i>b</i>, and the third cylindrical lenses <b>163</b> are formed in parallel with each other on the second surface <b>160</b><i>b</i>. In addition, the third cylindrical lenses <b>163</b> are parallel with the second cylindrical lenses <b>162</b>. Each of the second cylindrical lenses <b>162</b> and each of the third cylindrical lenses <b>163</b> are alternately arranged. It is note that the thickness T<b>2</b> of each of the second cylindrical lenses <b>162</b> is greater than the thickness T<b>3</b> of each of the third cylindrical lenses <b>163</b>.

In one example, on the first surface <b>160</b><i>a</i>, each of the first cylindrical lenses <b>161</b> adjoins another one of the first cylindrical lenses <b>161</b>. On the second surface <b>160</b><i>b</i>, each of the second cylindrical lenses <b>162</b> adjoins one of the third cylindrical lenses <b>162</b>.

In another example, the width W<b>1</b> of each of the first cylindrical lenses <b>161</b> is greater than the width W<b>2</b> of each of the second cylindrical lenses <b>162</b>, and each of the second cylindrical lenses <b>162</b> is arranged at a position opposite to a common adjoining edge between two adjoined first cylindrical lenses <b>161</b>.

In still another example, the radius of curvature R<b>1</b> of each of the first cylindrical lenses <b>161</b> is greater than the radius of curvature R<b>2</b> of each of the second cylindrical lenses <b>162</b>. Furthermore, the radius of curvature R<b>2</b> of each of the second cylindrical lenses <b>162</b> is different from the radius of curvature R<b>3</b> of each of the third cylindrical lenses <b>163</b>.

In one embodiment, as depicted in <figref idref="DRAWINGS">FIG. 1A</figref>, the electrophoretic display apparatus <b>100</b> may further comprise a lens <b>134</b>. The lens <b>134</b> may be a convex lens, for example, disposed between the light source <b>130</b> and the light receiving surface <b>122</b>, and is configured to convert the light emitted from the light source <b>130</b> into a parallel light beam.

<figref idref="DRAWINGS">FIG. 2A</figref> is cross-sectional view schematically illustrating an electrophoretic display apparatus <b>100</b>′ according to another embodiment of the present disclosure. The electrophoretic display apparatus <b>100</b>′ includes an electrophoretic display panel <b>110</b>, a collimated light guide <b>120</b>, a light source <b>130</b>, a light-splitting element <b>140</b>′ and a lens element <b>160</b>′. The electrophoretic display apparatus <b>100</b>′ has a structure similar to that of the embodiment depicted in <figref idref="DRAWINGS">FIG. 1A</figref>. However, the light-splitting element <b>140</b>′ and the lens element <b>160</b>′ of the electrophoretic display apparatus <b>100</b>′ is different from that of the electrophoretic display apparatuses <b>100</b> depicted in <figref idref="DRAWINGS">FIG. 1A</figref>. In the embodiment depicted in <figref idref="DRAWINGS">FIG. 2A</figref>, the electrophoretic display panel <b>110</b>, the collimated light guide <b>120</b>, the light source <b>130</b> may be the same as these described above in connection with <figref idref="DRAWINGS">FIG. 1A</figref>.

In the embodiment depicted in <figref idref="DRAWINGS">FIG. 2A</figref>, the light-splitting element <b>140</b>′ includes a diffraction grating <b>144</b> that is in contact with the light emitting surface <b>124</b>. The light emitted from the light emitting surface <b>124</b> has different wavelengths. When the light with different wavelengths passes through the diffraction grating <b>144</b>, it is split into a first, a second and a third light beam <b>150</b>R, <b>150</b>G, <b>150</b>B that travel in different directions. Each of the first, second and third light beams <b>150</b>R, <b>150</b>G, <b>150</b>B has a principal wavelength different from that of another one of the first, second and third light beams <b>150</b>R, <b>150</b>G, <b>150</b>B. Additionally, in this embodiment, the lens element <b>160</b>′ is an aspherical lens array. <figref idref="DRAWINGS">FIG. 2B</figref> is a perspective view showing the aspherical lens array according to one example of the present disclosure. The aspherical lens array is comprised of a plurality of a number of aspheric lenses <b>164</b>. The aspherical lens array is configured to direct the first, second and third light beams <b>150</b>R, <b>150</b>G, <b>150</b>B respectively to corresponding sub-pixels.

<figref idref="DRAWINGS">FIG. 3A</figref> is a top view schematically illustrating a light-splitting element <b>140</b>′ according to still another embodiment of the present disclosure. The light-splitting element <b>140</b>′ at least includes a first refraction grating array <b>170</b> and a second refraction grating array <b>180</b>, in which the first refraction grating array <b>170</b> and the second refraction grating array <b>180</b> are spaced apart by a spacing G. The first refraction grating array <b>170</b> has a plurality of first prisms <b>171</b>. Each of the first prisms <b>171</b> has a first crest line <b>171</b>T that is parallel to a first direction D<b>1</b>, and these first prisms <b>171</b> are arranged in a regular manner. Specifically, each first crest line <b>171</b>T is separated from an adjacent first crest line <b>171</b>T by a first pitch distance P<b>1</b>. Similarly, the second refraction grating array <b>180</b> has a plurality of second prisms <b>182</b>. Each of the second prisms <b>182</b> has a second crest line <b>182</b>T that is parallel to a second direction D<b>2</b>, and each second crest line <b>182</b>T is separated from an adjacent second crest line <b>182</b>T by a second pitch distance P<b>2</b>. In this embodiment, the first direction D<b>1</b> is not parallel with the second direction D<b>2</b>. For instance, the first direction D<b>1</b> may be perpendicular to the second direction D<b>2</b>, as depicted in <figref idref="DRAWINGS">FIG. 3A</figref>. Alternatively, the included angle between the first direction D<b>1</b> and the second direction D<b>2</b> may be about 5 degrees to 85 degrees, as depicted in <figref idref="DRAWINGS">FIG. 3B</figref>. In another embodiment, the first pitch distance P<b>1</b> is not equal to the second pitch distance P<b>2</b>. According to the embodiments in connection with <figref idref="DRAWINGS">FIG. 3A</figref> and <figref idref="DRAWINGS">FIG. 3B</figref>, the spectrum pattern generated by the light-splitting element <b>140</b>′ may be modulated. Particularly, when the light emitted from the collimated light guide <b>120</b> passes through the light-splitting element <b>140</b>, it may be split into several light beams with different principal wavelengths, and thus generating a spectrum pattern. However, in some embodiments, the spectrum pattern is undesirably rotated or deformed. Accordingly, the embodiments described above are intended to modulate the rotated or deformed spectrum pattern such that the lens element <b>160</b>′ may correctly direct the first, second and third light beams <b>150</b>R, <b>150</b>G, <b>150</b>B to corresponding sub-pixels.

It will be apparent to those skilled in the art that various modifications and variations can be made to the structure of the present invention without departing from the scope or spirit of the invention. In view of the foregoing, it is intended that the present invention cover modifications and variations of this invention provided they fall within the scope of the following claims.